Metadata is additional data that describes the actual data. For example, metadata can be used in file systems to describe where the corresponding data is stored. Cluster file systems, for example, allow multiple client devices to share access to files over a network. For many cluster file systems, especially for High Performance Computing (HPC) applications such as the Linux-based Lustre file system or the General Parallel File System (GPFS) developed by IBM Corp., the metadata servers (MDSs) are a bottleneck that reduce performance gains that would otherwise be available due to the intended parallel data access.
A number of techniques have been proposed or suggested to improve metadata access using distributed metadata servers. U.S. patent application Ser. No. 14/663,634, filed Mar. 20, 2015 (now U.S. Pat. No. 9,852,146), entitled “Distributed Metadata Servers for Cluster File Systems Using Shared Low Latency Persistent Key-Value Metadata Store,” incorporated by reference herein, discloses a cluster file system having a plurality of distributed metadata servers with shared access to one or more shared low latency persistent key-value metadata stores.
A need therefore exists for improved metadata servers using separate metadata servers for file metadata and directory metadata.